1. Field of the Invention
The present invention relates to a thermal printer suitable for printing on recording media by selectively generating heat from a plurality of heating elements of a thermal head on the basis of printing information.
2. Description of the Related Art
A heat transfer printer will now be described as a conventional thermal printer. Referring to FIG. 5, in the thermal printer 51, a paper guide plate 52b is formed in a slanted direction on the right side of a bottom plate 52a of a main body case 52, and recording media 53 can be fed in the direction of arrow A on the paper guide plate 52b. 
In addition, a cylindrical platen roller 54 is rotatably provided on the left side of the paper guide plate 52b. 
A thermal head 55 composed of a line head is provided on the upper side of the platen roller 54 to be opposite thereto.
The thermal head 55 is fixed to a head mount 56, and the head mount 56 is mounted on a head lever 57.
A circular supporting hole 57a is formed at one end of the right side of the head lever 57, and the other end of the head lever 57, on which the thermal head 55 has been mounted, can rotate using the supporting hole 57a as a shaft.
A pair of head levers 57 is provided to face each other and supports both ends of the head mount 56 on which the thermal head 55 is mounted.
Side plates 52c are provided in the main body case 52 to face each other, and the supporting holes 57a are supported by supporting shafts 58 fixed to the side plates 52, so that the head levers 57 can rotate.
The thermal head 55 is lifted or lowered by allowing the head levers 57 to rotate in the up and down directions with the supporting holes 57a as shafts and thus contact with or separates from the platen roller 54.
A paper transfer roller 60 and a pressure roller 61, which comes into pressure contact with the paper transfer roller 60, are provided on the lower side of the platen roller 54 in the feeding direction of arrow A. The pressure roller 61 is rotatably supported to a roller supporting case 62.
An ink ribbon 63 is wound up between the platen roller 54 and the thermal head 55 in a head-up state. The ink ribbon 63 is accommodated in a ribbon cassette 64 with both its ends wound up on a winding core 65 and a supply core 66, respectively.
In addition, the winding core 65 and the supply core 66 are engaged with a winding bobbin 67 and a supply bobbin 68 provided on one side plate 52c of the main body case 52, respectively.
A paper discharge roller 69 for discharging recording media 53 after printing is provided on the lower side of the winding core 65 in the feeding direction of arrow A.
The printing operation of a conventional thermal printer 51 will now be explained. The head levers 57 rotate upwardly to lift the thermal head 55, and the ribbon cassette 64 is mounted thereto.
Then, the recording media 53 is fed between the thermal head 55 in a head-up state and the platen roller 54 in the direction of arrow A.
The recording media 53 passing between the thermal head 55 and the platen roller 54 is sandwiched between the paper transfer roller 60 and the pressure roller 61, and the thermal head 55 is lowered.
A plurality of heating elements of the thermal head 55 makes pressure contact with the outer circumferential surface of the platen roller 54 with the recording media 53 and the ink ribbon 63 interposed therebetween.
Thereafter, the heating elements of the thermal head 55 are selectively made to generate heat on the basis of printing information, and the paper transfer roller 60 is rotated in a counterclockwise direction to feed the recording media 53 in the direction of arrow A. Accordingly, the desired color images are printed on the recording media 53.
In addition, the recording media 53, which passes between the paper transfer roller 60 and the pressure contact roller 61 after printing, is externally discharged by the paper discharge roller 69 rotating in the counterclockwise direction.
[Patent Document 1]
Japanese Unexamined Patent Application Publication No. 2002-79701
Japanese Unexamined Patent Application Publication No. 2002-120446
However, in the aforementioned conventional thermal printer 51, positional errors of the supporting holes 57a of the pair of head levers 57 or the thermal head 55 in the up and down directions may occur due to a difference in size between the head levers 57 or faults in assembly.
When the circular supporting holes 57a of the head levers 57 having such positional errors are supported by the supporting shafts 58, both sides of a long thermal head 55 are inclined in the up and down directions, and thus the thermal head 55 inclines in the longitudinal direction of the platen roller 54. Therefore, it was determined that the thermal head 55 could not uniformly make pressure contact with the platen roller 54.
Furthermore, when the thermal head 55 does not uniformly make pressure contact with the platen roller 54, printing quality on the recording media 53 can deteriorate.